In conventional combines, crop is threshed and separated by the use, in combination, of a threshing cylinder, a beater, straw walkers and a cleaner. Crop typically passes from a gathering mechanism through a table auger and a feeder elevator to the entrance portion of the threshing cylinder which is mounted transversely to the longitudinal frame axis of the combine. The threshing cylinder comprises a rotor rotatable within a concave and has metal rasp bars attached thereto to thresh the crop as it passes between the rasp bars and the concave of the threshing cylinder. A beater is positioned rearwardly of the threshing cylinder and its axis is substantially parallel to the axis of the threshing assembly. It further removes many of the free kernels that have not yet been separated from the crop in the threshing cylinder and also directs the crop to the straw walkers. The straw walkers convey the crop residue to the rearward and exit portions of the combine while removing free kernels and grain heads which have not been previously separated from the crop. A cleaner is located below the straw walkers and comprises a chaffer located in a higher position and a sieve located beneath the chaffer. The chaffer allows grain to drop therethrough and is adapted to remove the chaff because of its lighter weight and the effect of air flow. The chaffer also provides for returning grain heads to the threshing cylinder for rethreshing. The sieve allows separated free kernels to pass therethrough and be collected by a clean grain auger which conveys the grain to an elevator which, in turn, transports the grain to a grain storage tank.
To remove the grain from the grain tank, a is used which is located within an unloading chute located on one side of the combine. The unloading chute allows grain to be moved from the grain tank to an unloading or receiving vehicle positioned on the side of the combine where the exit portion of the unloading chute is located.
There are improvements possible in the conventional system just described. For example, the concave of the threshing cylinder surrounds it for only a relatively small portion of the more than 360.degree. which could be utilized to thresh and separate the crop. This is inefficient.
Similarly, as the quantity of material passing through a conventional combine is increased, there is a loss of efficiency in the straw walkers which increases disproportionately to the increased quantity of crop entering the combine. Free kernels and grain heads escape from the combine without being separated from the crop. This is clearly undesirable.
Manufacturers have attempted to increase the efficiency of grain removal from crop by utilizing "rotary" combines, so called because the crop circles the threshing and separating assembly through one or more revolutions rather than passing over only a portion thereof. Because of the increase in threshing and separating efficiency in rotary combines, the straw walkers may be eliminated. Nevertheless, many improvements are possible in present rotary combines.
For example, although the concave or grate extends over 360.degree. of the threshing cylinder which increases the separation efficiency of the combine, it also increases the quantity of very short and light pieces. This makes baling difficult
Similarly, present rotary designs usually require the crop to be introduced axially to the threshing and separating assembly. The incoming crop, therefore, must necessarily turn through an angle which will allow the crop flow to match the angle of the helical guide vanes which convey the crop through the assembly. This requirement may cause unnecessary congestion at the entrance area of the assembly which limits the combine feed rate. This, in turn, adversely affects combine capacity.
Yet a further problem relates to the feed path of crop. Present rotary combine designs usually call for the crop to travel a single path through the combine. In heavy crop conditions, this may limit the feed rate of crop material, particularly at the entrance areas, which again adversely affects combine capacity.
In conventional and rotary combines the unloading chute is located on one side of the combine. There may be no or limited rotational adjustment for the unloading chute available to the operator and, at any rate, the combine must be unloaded on one side only. In normal crop combining applications, the grain receiving vehicle necessarily drives through the swath causing undesirable crop damage. Similarly, the unloading flexibility of the operator may be limited by creating unnecessary vehicle movement when two trucks are deployed.
More recently, some of these problems were overcome or substantially improved by the rotary combine of our U.S. Pat. No. 4,117,849 (Pakosh). In the combine there disclosed, separate threshing and separator assemblies were utilized for greater efficiency. Crop was introduced along a plane substantially tangential to the entrance portion of the threshing cylinder which enabled the combine to process a greater amount of crop because the angle of the helical guide vanes located on the upper half of the casing was more closely aligned with the incoming angle of the crop thereby avoiding subjecting the crop to a large "turn" angle. A further improvement disclosed there was the introduction of crop at the central portion of the threshing assembly with the helical guide vanes on the casing acting to split the crop upon its introduction to the threshing cylinder. This increased the capacity of the combine because dividing the crop allowed the machine to handle more crop more efficiently in the threshing assembly.